Functionalized D-phenylalanine bis-Schiff base corrosion inhibitor as well as preparation method and application thereof

Abstract

The invention relates to the technical field of corrosion inhibitor synthesis, in particular to a functionalized D-phenylalanine bis-Schiff base corrosion inhibitor as well as a preparation method and application thereof. The preparation method comprises the following steps: dissolving D-phenylalanine in an ethanol-DMSO solution, heating and refluxing in an oil bath pan, and stirring and dissolving to form a solution A; dropwise adding an ethanol solution of terephthalaldehyde into the solution A, continuously heating and refluxing, and stirring to form a solution B; adding phosphoric acid into the solution B, continuously heating, stirring and refluxing, and carrying out nucleophilic addition reaction to obtain the D-phenylalanine bis-Schiff base. And cooling the D-phenylalanine bis-Schiff base to room temperature, removing impurities, and drying to obtain the functionalized D-phenylalanine bis-Schiff base corrosion inhibitor. The functionalized D-phenylalanine bis-Schiff base corrosion inhibitor has nitrogen, oxygen and benzene ring adsorption sites, lone electron pairs can be provided to form coordinate bonds with iron atoms, corrosion inhibitor molecules can be better adsorbed on the metal surface, and the corrosion process is slowed down.

Description

Technical Field

[0001] The present invention relates to the technical field of corrosion inhibitor synthesis, and in particular to a functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor, and a preparation method and application thereof. Background Art

[0002] The global annual corrosion loss is as high as 1.8 trillion US dollars. Corrosion inhibitors are widely used as an economical and efficient means of protection. Corrosion inhibitors can effectively reduce the economic losses caused by corrosion and ensure the normal operation of industrial equipment. Among them, the -C=N- functional group of Schiff base has good stability and excellent coordination ability. Most Schiff bases also have atoms such as O and S that have donor electrons. The carbon steel surface is + The adsorption of Cl - Physical adsorption occurs on the carbon steel surface through Coulomb force; chemical adsorption occurs due to the presence of electron-rich N, O, S atoms and aromatic rings in the Schiff base structure.

[0003] There are four methods for synthesizing double Schiff base corrosion inhibitors, generally the dropwise addition method. The first is the direct synthesis method, in which aldehydes and amines are directly mixed and reacted in a certain proportion. This method has a higher yield, but there are more side reactions and the product treatment is more complicated. The second is the step-by-step reaction method, in which a fresh Schiff base solution is first prepared and then a metal salt is added. This method can reduce the formation of by-products by controlling the reaction conditions. The third is the template synthesis method, which is suitable for situations where the reactant activity is low or the product is unstable. Metal ions are used as templates to improve the yield and conversion rate, and are easy to separate and purify. The fourth is the dropwise addition method, in which the amine compound is first mixed with the metal ion solution, and then the aldehyde or ketone solution is added dropwise, and stirred vigorously to form a complex.

[0004] Currently reported bis-Schiff base corrosion inhibitors include 2-pyridinecarboxaldehyde-based Schiff bases and 2-(4-(dimethylamino)-benzylimino)benzenethiol. These exhibit poor corrosion inhibition performance at low concentrations. However, there are very few reports on the preparation of bis-Schiff base corrosion inhibitors using D-phenylalanine as a nitrogen source. Therefore, developing a carbon dot corrosion inhibitor that uses D-phenylalanine as a nitrogen source, exhibits simple preparation processes, and exhibits excellent corrosion inhibition performance, is of great research significance and market value. Summary of the Invention

[0005] The purpose of the present invention is to provide a functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor and its preparation method and application, which can solve the above technical problems.

[0006] The present invention provides a method for preparing a functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor, comprising the following steps:

[0007] S1. Dissolve D-phenylalanine in an ethanol-DMSO solution, heat to reflux, and stir to dissolve to form solution A;

[0008] S2. Add terephthalaldehyde in ethanol solution dropwise to solution A, continue heating under reflux and stirring to form solution B;

[0009] S3. Phosphoric acid was added to solution B, and heating and stirring were continued to perform a nucleophilic addition reaction to prepare a D-phenylalanine-based bis-Schiff base;

[0010] S4. After cooling the D-phenylalanine-based bis-Schiff base obtained in step S3 to room temperature, removing impurities and drying are performed to obtain a functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor.

[0011] Preferably, the mass ratio of D-phenylalanine to terephthalaldehyde in step S1 and step S2 is (1.7-3.4): (0.5-1.25).

[0012] Preferably, in step S1, the mass volume ratio of D-phenylalanine, ethanol and DMSO is (1.7-3.4) g: (30-60) ml: (10-20) ml.

[0013] Preferably, the mass volume ratio of terephthalaldehyde to ethanol in the ethanol solution of terephthalaldehyde in step S2 is (0.5-1.25) g: (50-100) ml.

[0014] Preferably, in step S3, the volume ratio of phosphoric acid to solution B is: (0.9-1.8): (90-180), and the mass fraction of the phosphoric acid is 85%.

[0015] Preferably, the oil bath is heated in step S1 at a temperature of 70-80° C.; and the heating, reflux, and stirring time in step S3 is 6-8 hours.

[0016] Preferably, the specific steps of removing impurities in step S4 are: first filtering, then washing the D-phenylalanine-based bis-Schiff base with ethanol multiple times, and performing rotary evaporation separation at 50° C. after each washing to complete the impurity removal.

[0017] Preferably, the specific steps of drying in step S4 are: air-drying under natural conditions for 2-3 days to complete drying.

[0018] The present invention also provides a functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor prepared by the above preparation method.

[0019] The present invention also provides a use of the functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor in preventing corrosion of N80 carbon steel material.

[0020] Beneficial effects:

[0021] The functionalized D-phenylalanine-based double-Schiff base corrosion inhibitor of the present application has oxygen, benzene ring and nitrogen adsorption sites, can provide lone pair of electrons to form coordination bond with iron atom, and makes the corrosion inhibitor molecule better adsorbed on the metal surface, thereby slowing down the corrosion process.

[0022] The functionalized D-phenylalanine-based double-Schiff base corrosion inhibitor of the present application belongs to high-efficiency corrosion inhibitor, exhibits good corrosion inhibition effect, and is yellow powder at normal temperature. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0024] Figure 1 The Fourier transform infrared absorption spectrum of the functionalized D-phenylalanine corrosion inhibitor sample prepared in Example 1 of the present application is shown in the figure;

[0025] Figure 2 The figure is a schematic diagram of a three-electrode test system;

[0026] Figure 3 The figure is an electrochemical impedance spectrum of N80 carbon steel in 1mol / L hydrochloric acid solution added with different concentrations of the functionalized D-phenylalanine-based double-Schiff base corrosion inhibitor prepared in Example 2;

[0027] Figure 4 The figure is an equivalent circuit diagram corresponding to the electrochemical impedance spectrum in Test Example 1 of the present application;

[0028] Figure 5 The figure is a polarization curve of N80 carbon steel immersed in 1mol / L hydrochloric acid solution added with different concentrations of the functionalized D-phenylalanine-based double-Schiff base corrosion inhibitor prepared in Example 2 for 1h;

[0029] Figure 6Polarization curves of N80 carbon steel immersed in 1 mol / L hydrochloric acid solution to which 0 mg / L and 500 mg / L of the functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor prepared in Example 2 were added at different temperatures for 1 h. DETAILED DESCRIPTION

[0030] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0031] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular also includes the plural. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0032] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] Example 1:

[0034] A method for preparing a functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor comprises the following steps:

[0035] S1. Dissolve 1.70 g of D-phenylalanine in 40 ml of ethanol-DMSO solution (30 ml of ethanol + 10 ml of DMSO). Heat in an oil bath under reflux to 70°C and stir to form solution A.

[0036] S2. A 50 ml ethanol solution of 0.50 g of terephthalaldehyde was added dropwise to solution A (a solution formed by adding 0.50 g of terephthalaldehyde to 50 ml of ethanol), and the mixture was heated under reflux with stirring to form solution B;

[0037] S3. 0.90 ml of phosphoric acid (85%) was added to solution B and the mixture was heated under reflux with stirring for 6 h. After a nucleophilic addition reaction, a D-phenylalanine-based bis-Schiff base was prepared;

[0038] S4. The D-phenylalanine-based bis-Schiff base obtained in step S3 was cooled to room temperature, filtered, and then rinsed with ethanol three times. After each rinse, rotary evaporation was performed at 50°C to complete impurity removal. The product was air-dried under natural conditions for 2 days to obtain a functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor.

[0039] Example 2

[0040] A method for preparing a functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor comprises the following steps:

[0041] S1. Dissolve 2.55 g of D-phenylalanine in 60 ml of ethanol-DMSO solution (45 ml of ethanol + 15 ml of DMSO). Heat in an oil bath to reflux at 75°C and stir to form solution A.

[0042] S2. 0.75 g of terephthalaldehyde in 75 ml of ethanol was added dropwise to solution A, and the mixture was heated under reflux with stirring to form solution B;

[0043] S3. 1.35 ml of phosphoric acid (85%) was added to solution B and the mixture was heated under reflux with stirring for 7 h. After a nucleophilic addition reaction, a D-phenylalanine-based bis-Schiff base was prepared;

[0044] S4. The D-phenylalanine-based bis-Schiff base obtained in step S3 was cooled to room temperature, filtered, and then rinsed with ethanol three times. After each rinse, rotary evaporation was performed at 50°C to complete impurity removal. The product was air-dried under natural conditions for 2 days to obtain a functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor.

[0045] Example 3

[0046] A method for preparing a functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor comprises the following steps:

[0047] S1. Dissolve 3.4 g of D-phenylalanine in 80 ml of ethanol-DMSO solution (60 ml of ethanol + 20 ml of DMSO). Heat in an oil bath under reflux to 80°C and stir to form solution A.

[0048] S2. 1.25 g of terephthalaldehyde in 100 ml of ethanol was added dropwise to solution A, and the mixture was heated under reflux with stirring to form solution B;

[0049] S3. 1.8 ml of phosphoric acid (85%) was added to solution B and the mixture was heated under reflux with stirring for 8 h. After a nucleophilic addition reaction, a D-phenylalanine-based bis-Schiff base was prepared;

[0050] S4. The D-phenylalanine-based bis-Schiff base obtained in step S3 was cooled to room temperature, filtered, and then rinsed with ethanol three times. After each rinse, rotary evaporation was performed at 50°C to complete impurity removal. The product was air-dried under natural conditions for 3 days to obtain a functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor.

[0051] Fourier transform infrared spectroscopy characterization: The functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor prepared in Example 1 was subjected to infrared spectroscopy analysis, and the Fourier transform infrared absorption spectrum was obtained as shown in the following figure: Figure 1 As shown. Figure 1 It can be seen that the infrared absorption spectrum of the functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor prepared in Example 1 of the present invention contains different absorption bands, 3420-2554 cm -1 The stretching vibration peaks of OH and benzene ring -CH appeared in the range of 1688.41cm -1 The characteristic peak of carboxyl C=O appeared at 1503.08 cm -1 and 1412.34cm -1 The peak of the benzene ring skeleton is at 849.44 cm -1 The peak at 1588.54 cm is the characteristic peak of benzene ring substitution. -1 and 1620.30cm -1 The nearby peak is the stretching vibration absorption peak of -C=N-. The results show that the functionalized D-phenylalanine-based double Schiff base corrosion inhibitor structure was successfully synthesized by the dropwise addition method.

[0052] The functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor prepared in Example 2 of the present invention was evaluated by an electrochemical method.

[0053] Test Example 1: The electrochemical workstation is CS310H, and the test adopts a three-electrode system: the working electrode is made of N80 carbon steel, the reference electrode is a saturated calomel electrode, and the auxiliary electrode is a platinum electrode. Figure 2 As shown. N80 carbon steel is encapsulated with epoxy resin into a cylindrical electrode. The electrode is encapsulated on one end of the epoxy resin and welded to a copper wire to lead out the conductive circuit. The exposed area of ​​the working electrode is 1.0 cm 2 Except for the exposed surface in contact with the solution, the other end surfaces were encapsulated with epoxy resin. The exposed surface of the working electrode was polished with 240, 600 and 1200 mesh SiC sandpaper, then cleaned with deionized water and anhydrous ethanol, dried with cold air and placed in a vacuum desiccator for later use. The AC impedance test frequency was 10 -2 ~10 4Hz, with an amplitude of 5 mV. The experiment was carried out in 1 mol / L hydrochloric acid solution, and five groups were set, in which the inhibitor concentrations were 0 mg / L, 50 mg / L, 100 mg / L, 300 mg / L and 500 mg / L, respectively, and the experimental temperature was 25°C. After the open circuit potential reached stability, the test was started. The alternating current impedance spectrum of N80 carbon steel in 1M HCl solution with different concentrations of functionalized D-phenylalanine-based bis-Schiff base inhibitor was obtained by test Figure 3 .

[0054] Then the above impedance spectrum was fitted using the equivalent circuit diagram shown in Figure 4 , and the inhibition efficiency was calculated, and the inhibition efficiency was calculated by formula (1):

[0055]

[0056] In the formula: IE EIS is the inhibition efficiency, %; is the charge transfer resistance of the blank group, Ω; R ct is the charge transfer resistance after adding the inhibitor, Ω.

[0057] The fitting results of the alternating current impedance spectrum of N80 carbon steel in 1 mol / L hydrochloric acid solution with different concentrations of functionalized D-phenylalanine-based bis-Schiff base inhibitor are shown in Table 1.

[0058] Table 1

[0059]

[0060] In the table: C is the inhibitor concentration, mg / L; R s is the solution resistance, Ω; CPE is the constant phase element; R p is the charge transfer resistance, Ω; η is the inhibition efficiency, %.

[0061] From the fitting data shown in Table 1, it can be seen that the charge transfer resistance of the blank group without adding the inhibitor is small, indicating that the metal surface has undergone serious corrosion. After adding different concentrations of functionalized D-phenylalanine-based bis-Schiff base inhibitor, the charge transfer resistance increases significantly, indicating that the functionalized D-phenylalanine-based bis-Schiff base inhibitor can effectively inhibit the corrosion of the metal. When the concentration of the inhibitor is 500 mg / L, the inhibition efficiency of the functionalized D-phenylalanine-based bis-Schiff base inhibitor is best, reaching 96.51%.

[0062] Test Example 2: The polarization curve of N80 carbon steel in 1 mol / L hydrochloric acid solution with different concentrations of functionalized D-phenylalanine-based bis-Schiff base inhibitor was measured according to the method described in Test Example 1, the scanning range was relative to the open circuit potential ±220 mV, the scanning rate was 0.5 mV / s, and the sampling frequency was 1 Hz. The obtained polarization curve is as shown in Figure 5As shown, the corrosion inhibition efficiency is calculated using formula (2):

[0063]

[0064] Where: η is the corrosion inhibition efficiency, %; is the corrosion current of the blank control group after immersion for 1 hour, Amp / cm 2 ;I O The corrosion current after immersion for 1 hour after adding functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor, Amp / cm 2 .

[0065] The fitting results of the polarization curves of N80 carbon steel after immersion in 1 mol / L hydrochloric acid solution with different concentrations of functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor for 1 h are shown in Table 2.

[0066] Table 2

[0067] C (mg / L) <![CDATA[I o (Amp / cm 2 )]]> <![CDATA[E o (Volts)]]> Corrosion inhibition efficiency η(%) 0 <![CDATA[7.06×10 -4 ]]> -0.45 - 50 4.48 x 10 -5 ]]> -0.44 93.65 100 <![CDATA[3.85×10 -5 ]]> -0.44 94.55 300 <![CDATA[3.83×10 -5 ]]> -0.41 94.58 500 <![CDATA[3.38×10 -5 ]]> -0.42 95.21

[0068] In the table: C is the concentration of corrosion inhibitor, mg / L; E o is the corrosion potential, Volts; I o is the corrosion current, Amp / cm 2 ; η is the corrosion inhibition efficiency, %.

[0069] As shown in Table 2, the addition of the functionalized D-phenylalanine-based bis-Schiff base inhibitor reduced the corrosion current of N80 carbon steel, indicating that the functionalized D-phenylalanine-based bis-Schiff base inhibitor has a significant inhibitory effect. When the inhibitor concentration is 50 mg / L, the inhibition efficiency can reach 93.65%.

[0070] Test Example 3: The polarization curves of N80 carbon steel in 1 mol / L hydrochloric acid solution with different concentrations of functionalized D-phenylalanine-based bis-Schiff base were measured at different temperatures according to the method described in Test Example 2. The scanning range was ±220 mV relative to the open circuit potential, the scanning rate was 0.5 mV / s, and the sampling frequency was 1 Hz. The obtained polarization curves are shown in Figure 2. Figure 6 As shown, the corrosion inhibition efficiency is calculated using formula (2);

[0071] The fitting results of the polarization curves of N80 carbon steel immersed in 1 mol / L hydrochloric acid solution with 0 mg / L and 500 mg / L functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor at different temperatures for 1 h are shown in Table 3.

[0072] Table 3

[0073]

[0074] In the table: C is the concentration of corrosion inhibitor, mg / L; T is the Kelvin temperature, K; Eo is the corrosion potential, Volts; I o is the corrosion current, Amp / cm 2 ; η is the corrosion inhibition efficiency, %.

[0075] As can be seen from Table 3, after adding the functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor, the corrosion current of N80 carbon steel will increase with increasing temperature, but the corrosion inhibition efficiency is still 93.95% at 45°C when the corrosion inhibitor concentration is 500 mg / L, indicating that the D-phenylalanine-based bis-Schiff base corrosion inhibitor has a significant inhibitory effect.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor, characterized in that: The following steps are involved: S1. Dissolve D-phenylalanine in an ethanol-DMSO solution, heat to reflux, and stir to dissolve to form solution A; S2. Add terephthalaldehyde in ethanol solution dropwise to solution A, continue heating under reflux and stirring to form solution B; S3. Phosphoric acid was added to solution B, and heating and stirring were continued to perform a nucleophilic addition reaction to prepare a D-phenylalanine-based bis-Schiff base; S4. After cooling the D-phenylalanine-based bis-Schiff base obtained in step S3 to room temperature, removing impurities and drying are performed to obtain a functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor.

2. The method for preparing the functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor according to claim 1, wherein: The mass ratio of D-phenylalanine to terephthalaldehyde in step S1 and step S2 is (1.7-3.4): (0.5-1.25).

3. The method for preparing the functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor according to claim 1, wherein: The mass volume ratio of D-phenylalanine, ethanol and DMSO in step S1 is (1.7-3.4) g: (30-60) ml: (10-20) ml.

4. The method for preparing the functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor according to claim 1, wherein: In the ethanol solution of terephthalaldehyde in step S2, the mass volume ratio of terephthalaldehyde to ethanol is (0.5-1.25) g: (50-100) ml.

5. The method for preparing the functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor according to claim 1, wherein: In step S3, the volume ratio of phosphoric acid to solution B is (0.9-1.8): (90-180), and the mass fraction of the phosphoric acid is 85%.

6. The method for preparing the functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor according to claim 1, wherein: In step S1, the oil bath is heated at a temperature of 70-80° C.; in step S3, the heating reflux stirring time is 6-8 hours.

7. The method for preparing the functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor according to claim 1, wherein: The specific steps of removing impurities in step S4 are: first filtering, then washing the D-phenylalanine-based bis-Schiff base with ethanol multiple times, and performing rotary evaporation separation at 50° C. after each washing to complete the impurity removal.

8. The method for preparing the functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor according to claim 1, wherein: The specific steps of drying in step S4 are: air-drying under natural conditions for 2-3 days to complete the drying.

9. A functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the functionalized D-phenylalanine-based bis-Schiff base corrosion inhibitor according to claim 9 in preventing corrosion of N80 carbon steel material.

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